Such a rotor is described in particular in French patent FR 2 685 675 and U.S. Pat. No. 5,330,322.
The invention applies more particularly to a rotor of that type in which the twistable structure is secured to the hub by clamping the twistable structure between two parts of the hub, using a bolt associated with a washer or ring for transmitting a clamping force.
It has been found that under certain circumstances, during tightening of the nut and/or the bolt, the washer or ring can be caused to turn due to friction against the nut, and that this turning can lead to harmful deformation of the portion of the twistable structure through which the bolt extends, this deformation being more accentuated when the twistable structure is thin.